Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "James Bishop" <bishopaj@...> wrote:
>
> This gave me an idea.. I wonder if it would be possible to replace the
> laser diode in a laser printer with a uv one, and then run a
> sensitised board through in place of the drum..
> 
> What do you guys think? Am i crazy?

Not crazy. I recall a past conversation on this but don't recall the
outcome.

I suspect exposure time would be a problem. Photoconductor drums are
very sensitive, whereas photoresist is not.

Aha... found something relevant. Someone calculated how much exposure
time from a 2mW UV laser diode. Says approximately 25 seconds per
square cm minimum. Way to slow for a laser printer. High sensitivity
photoresist would require darkroom procedures.

http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/1933

It would also take a very large change in the mechanics of a laser
printer. A laser printer works by shining laser or LED light onto a
charged photoconductor drum, which causes charge to drain from the
exposed areas. The unexposed, still charged areas then attract toner
from another roller, then the paper is rolled across the
photoconductor drum with a high voltage behind the paper to attract
the toner to the paper. The paper then has a hot fuser roller melt the
toner onto it.

It seems that direct inkjet conversion would be much simpler,
comparatively.

But don't let anyone stop you from trying! There used to be lots of
nay-sayers about direct inkjet printing, some of them quite vehement.
All it really took to happen was the advent of pigmented ink and for
someone to keep trying.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, "Steve" <alienrelics@...> wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com, "James Bishop" <bishopaj@> wrote:
> >
> > This gave me an idea.. I wonder if it would be possible to replace the
> > laser diode in a laser printer with a uv one, and then run a
> > sensitised board through in place of the drum..
> > 
> > What do you guys think? Am i crazy?
> 
> Not crazy. I recall a past conversation on this but don't recall the
> outcome.
> 
> I suspect exposure time would be a problem. Photoconductor drums are
> very sensitive, whereas photoresist is not.
> 
> Aha... found something relevant. Someone calculated how much exposure
> time from a 2mW UV laser diode. Says approximately 25 seconds per
> square cm minimum. Way to slow for a laser printer. High sensitivity
> photoresist would require darkroom procedures.
> 
> http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/1933
> 
> It would also take a very large change in the mechanics of a laser
> printer. A laser printer works by shining laser or LED light onto a
> charged photoconductor drum, which causes charge to drain from the
> exposed areas. The unexposed, still charged areas then attract toner
> from another roller, then the paper is rolled across the
> photoconductor drum with a high voltage behind the paper to attract
> the toner to the paper. The paper then has a hot fuser roller melt the
> toner onto it.
> 
> It seems that direct inkjet conversion would be much simpler,
> comparatively.
> 
> But don't let anyone stop you from trying! There used to be lots of
> nay-sayers about direct inkjet printing, some of them quite vehement.
> All it really took to happen was the advent of pigmented ink and for
> someone to keep trying.
> 
> Steve Greenfield

I'd expect the optics to be a bit of a trick.  Note that the laser
diode in a laser printer is scanned, usually via either a rotating
mirror or a hologram, across the photoconductive drum.  Trying to 
focus a UV LED, and keep it pinpoint sharp as it traversed the 
different distances across the face of the drum, might be a bit of a 
trick (especially since UV is mostly invisible, and since some glass 
lenses tend to not do a good job of transmitting UV).  It could, of 
course, be made to work, given a sufficient design, but there'd still 
be concerns about the resolution causing broken traces.

I'd think that it might be easier to simply mount a UV LED on an 
X-Y plotter, and "draw" the design onto the PCB directly.  Of course, 
you'd have to control the slew speed of the "pen" to ensure that 
all areas were adequately exposed.  And, there'd be some optics 
design that would be needed, but this would be simplified since the
distance from the UV LED to the photosensitized board would remain
constant.  Plus, you'd need to rework the pen up/down solenoid so
that it controlled power to the UV LED.

If you really wanted to get fancy, you could probably work up some
interchangeable apertures for the UV LED to allow plotting different
sized lines (If you really wanted to get fancy, you could work this
into the pen up/down solenoid control.).  

Of course, this is basically reinventing a photo-plotter, which have
existed for decades.

Dave

--- In Homebrew_PCBs@yahoogroups.com, "Steve" <alienrelics@...> wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com, "James Bishop" <bishopaj@> wrote:
> >
> > This gave me an idea.. I wonder if it would be possible to replace the
> > laser diode in a laser printer with a uv one, and then run a
> > sensitised board through in place of the drum..
> > 
> > What do you guys think? Am i crazy?
> 
> Not crazy. I recall a past conversation on this but don't recall the
> outcome.
> 
> I suspect exposure time would be a problem. Photoconductor drums are
> very sensitive, whereas photoresist is not.
> 
...

> It seems that direct inkjet conversion would be much simpler,
> comparatively.
> 
> But don't let anyone stop you from trying! There used to be lots of
> nay-sayers about direct inkjet printing, some of them quite vehement.
> All it really took to happen was the advent of pigmented ink and for
> someone to keep trying.
> 
> Steve Greenfield
>

I too think that converting a laser printer would be difficult for the
reasons given.  A steered & focused laser *could* work. The refinement
of the technology physicists apply to manipulate Bose-Einstein
condensates & quantum entangled subatomic particles makes etching PCBs
seem quaint.  But it seems to me that the laser printer itself takes
too different an approach to printing to be reasonably modifiable.  I
*would* like to see someone prove me wrong, though!

What I was thinking of when I mentioned this was mounting a small
laser diode from a DVD burner in or in place of the inkjet head in a
salvaged printer, putting the whole works in a light proof box
(probably made out of black foamcore) and 'printing' directly on
photosensitized positive or negative type emulsion.  

Thinking further about this, it seems to me that the printer
(depending on the model chosen) would probably have the necessary X &
Y resolution.  The big advantage would be the ability to use the
existing printer driver for control.  The manufacturer has almost
certainly done a lot of tuning to manage microstepping, motor
resonances, etc.  The hard part might be fooling the print driver to
think that it has a functioning cartridge in place with a normal
supply of ink.

The distance between the print head and the emulsion would likely be
similar to but not the same as the gap between the DVD head and its
target.  The focal length of the diode's optics is probably not
optimal.  What may be important is the spot size at the emulsion.  Too
fine a focus might cause problems, too. The finer the focus the more
optical energy is deposited in a given volume of emulsion.  But too
fine a focus might create a halftone effect, depending on its
dispersive/absorptive properties. 

Rotating media use closed-loop servo mechanisms to control tracking
and make fine adjustments.  I believe they are working with much
tighter tolerances than we are, but I don't know.  Tuning the
intensity of the beam could be managed with simple pulse width
modulation of the laser.  I'm not sure what else might be involved, it
is probably time for some empirical tests.

-- Dave W

>What I was thinking of when I mentioned this was mounting a small
>laser diode from a DVD burner in or in place of the inkjet head in a
>salvaged printer, putting the whole works in a light proof box
>(probably made out of black foamcore) and 'printing' directly on
>photosensitized positive or negative type emulsion.

As I know it is IR not UV laser.
Cristian 

[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, Cristian <bip@...> wrote:
>
> 
> >What I was thinking of when I mentioned this was mounting a small
> >laser diode from a DVD burner in or in place of the inkjet head in a
> >salvaged printer, putting the whole works in a light proof box
> >(probably made out of black foamcore) and 'printing' directly on
> >photosensitized positive or negative type emulsion.
> 
> As I know it is IR not UV laser.
> Cristian 
> 
> [Non-text portions of this message have been removed]
>

I was planning to use one that I believe comes from a Blu-ray device.
 I believe that the one used for recording in early CDR's was IR, but
I don't know so much about more recent DVD, Dual layer, and high
density recording devices.  

What I ordered is supposed to be a 405 nm laser diode - not quite what
I consider UV, but close, and in a range that is at least somewhat
effective for many photoresist materials.

-- Dave w.

>What I ordered is supposed to be a 405 nm laser diode - not quite what
>I consider UV, but close, and in a range that is at least somewhat
>effective for many photoresist materials.

Right, this one will work.
Let me know where you find the right UV optics.
Cristian

>I was planning to use one that I believe comes from a Blu-ray device.
> I believe that the one used for recording in early CDR's was IR, but
>I don't know so much about more recent DVD, Dual layer, and high
>density recording devices.

     Yeah, generally CDR = IR, DVDR = both IR and Visible red, in two 
separate diodes, Blu-Ray = red and violet in the same component. - Insert 
laser safety paragraph here - .

     Interesting links:

http://www.fineartradiography.com/hobbies/lasers/blu-ray/index.html
http://www.die4laser.com/dvd-rec/DissectionofaDVDwriter.htm